“Baseline and follow-up 18F-FLT positron emission tomography/computed tomography images are shown of 2 patients with angiosarcoma of the breast. The patient shown in (A) exhibited >95% tissue necrosis after neoadjuvant treatment and was classified as a histopathologic responder. The patient in (B) was a histopathologic nonresponder with <5% tissue necrosis after treatment. However, comparable decreases in 18F-FLT uptake of 85% and 71%, respectively, were seen. Therefore, the patient in (B) was misclassified as a metabolic responder by fluorothymidine positron emission tomography analysis. SUVpeak indicates peak standardized uptake value”. Reprinted, with permission, from reference [27].